15-hydroxy-5-8-11-13-eicosatetraenoic-acid and Carcinoma--Non-Small-Cell-Lung

Peroxisome proliferator-activated receptor (PPAR)-α and PPARγ participate in cell proliferation and apoptosis. Few studies have simultaneously investigated both PPARα and PPARγ in lung cancers in vivo. The roles of PPARα and -γ were investigated in the development of pulmonary tumors induced in the adult A/J mouse by treatment with 4-(methylnitrosamino)-l-(3-pyridyl)-lbutanone (NNK). Compared with the normal lung tissues, PPARγ expression was much higher in the NNK-induced lung tumor tissues. However, PPARγ transcriptional activity, and the levels of two major endogenous PPARγ ligands, 13-hydroxyoctadecadienoic acid and 15-hydroxyeicosatetraenoic acid, were significantly lower in the NNK-treated lung tissues. The ligand changes in mice were confirmed in human lung cancer tissues. Along with the alteration of PPARγ and its endogenous ligands, the level of PPARα and its activity were increased in the NNK-induced mouse lung tumors. Treatment of mice with the synthetic PPARγ ligand, pioglitazone, significantly inhibited the formation of mouse lung tumors induced by NNK. Our study demonstrated that the reduction of endogenous PPARγ ligands and increased PPARα occurred before the formation of lung tumors, indicating that the molecular changes play a role in lung carcinogenesis. The results suggest that the enhancement of PPARγ activity with its ligands, and the suppression of PPARα with its inhibitors, may prevent the formation of lung tumors, as well as accelerate the therapy of lung cancer. Our findings may also reveal the possibility of using the level of endogenous PPARγ ligands and the activities of PPARγ or PPARα as tumor markers for lung cancer.

Topics: Animals; Carcinoma, Non-Small-Cell Lung; Disease Progression; Female; Gene Expression Regulation, Neoplastic; Humans; Hydroxyeicosatetraenoic Acids; Ligands; Linoleic Acids; Lipid Metabolism; Lung Neoplasms; Male; Mice; Nitrosamines; Pioglitazone; PPAR alpha; PPAR gamma; Precancerous Conditions; Retinoid X Receptor alpha; Signal Transduction; Thiazolidinediones; Transcription, Genetic

15-S-Hydroxyeicosatetraenoic acid (15(S)-HETE) and 13-S-hydroxyoctadecadienoic acid (13(S)-HODE), both of which are metabolites of 15-lipoxygenases (15-LOXs), are endogenous ligands for peroxisome proliferator-activated receptor gamma (PPARgamma). The activation of PPARgamma inhibits cell growth and induces apoptosis in some cancers. The role of 15(S)-HETE) and 13(S)-HODE in the development of lung cancer is not clear.. 15-LOXs, 15(S)-HETE and 13(S)-HODE were monitored during the development of mouse lung tumours induced by the tobacco smoke carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and the levels of these markers were determined in 54 human non-small cell lung cancers.. 15-LOXs, 15(S)-HETE and 13(S)-HODE levels were significantly reduced in human lung cancer tissue compared with non-tumour lung tissue (p=0.011 and p=0.022, respectively). In mouse experiments, 15(S)-HETE and 13(S)-HODE started to reduce at 26 and 30 weeks, respectively, after NNK treatment. The time frame of 15(S)-HETE reduction was in line with the decrease in 12/15-LOX mRNA and protein. A significant difference in the number of tumours in NNK-treated mice and controls was not observed until week 34 (p<0.05) and week 38 (p<0.01). The reduction in 12/15-LOX and 15(S)-HETE therefore predated the appearance of lung tumour. Furthermore, PPARgamma activity was decreased in NNK-treated mouse lungs compared with the control, and the decreased PPARgamma activity occurred at the same time points as the reduction in 12/15-LOX and 15(S)-HETE.. These findings indicate that the reduction in 15-LOX, 15(S)-HETE and 13(S)-HODE results in the decreased PPARgamma activity seen in lung tumours and contributes to the development of lung tumours induced by tobacco smoking.

Topics: Animals; Arachidonate 15-Lipoxygenase; Biomarkers, Tumor; Carcinoma, Non-Small-Cell Lung; Cell Transformation, Neoplastic; Disease Models, Animal; Disease Progression; Female; Humans; Hydroxyeicosatetraenoic Acids; Linoleic Acids; Lung; Lung Neoplasms; Mice; Mice, Inbred A; Neoplasm Proteins; Nitrosamines; PPAR gamma

Emerging preclinical data suggests that tea possess anticarcinogenic and antimutagenic properties. We therefore hypothesize that white tea extract (WTE) is capable of favorably modulating apoptosis, a mechanism associated with lung tumorigenesis. We examined the effects of physiologically relevant doses of WTE on the induction of apoptosis in non-small cell lung cancer cell lines A549 (adenocarcinoma) and H520 (squamous cell carcinoma) cells. We further characterized the molecular mechanisms responsible for WTE-induced apoptosis, including the induction of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and the 15-lipoxygenase (15-LOX) signaling pathways. We found that WTE was effective in inducing apoptosis in both A549 and H520 cells, and inhibition of PPAR-gamma with GW9662 partially reversed WTE-induced apoptosis. We further show that WTE increased PPAR-gamma activation and mRNA expression, concomitantly increased 15(S)-hydroxy-eicosatetraenoic acid release, and upregulated 15-LOX-1 and 15-LOX-2 mRNA expression by A549 cells. Inhibition of 15-LOX with nordihydroguaiaretic acid (NGDA), as well as caffeic acid, abrogated WTE-induced PPAR-gamma activation and upregulation of PPAR-gamma mRNA expression in A549 cells. WTE also induced cyclin-dependent kinase inhibitor 1A mRNA expression and activated caspase-3. Inhibition of caspase-3 abrogated WTE-induced apoptosis. Our findings indicate that WTE is capable of inducing apoptosis in non-small cell lung cancer cell lines. The induction of apoptosis seems to be mediated, in part, through the upregulation of the PPAR-gamma and 15-LOX signaling pathways, with enhanced activation of caspase-3. Our findings support the future investigation of WTE as an antineoplastic and chemopreventive agent for lung cancer.

Topics: Anilides; Apoptosis; Arachidonate 15-Lipoxygenase; Carcinoma, Non-Small-Cell Lung; Catechin; Drug Evaluation, Preclinical; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Neoplastic; Hormone Antagonists; Humans; Hydroxyeicosatetraenoic Acids; Lung Neoplasms; Plant Extracts; PPAR gamma; Tea; Tumor Cells, Cultured